Details of major Internet flaw posted by accident

A computer security company on Monday inadvertently published details of a major flaw in the Internet's DNS several weeks
before they were due to be disclosed

The flaw was
discovered several months ago by IOActive researcher Dan Kaminsky, who
worked through the early part of this year with Internet software
vendors such as Microsoft, Cisco, and the Internet Systems Consortium
to patch the issue.

The
companies released a fix for the bug two weeks ago and encouraged
corporate users and Internet service providers to patch their DNS
systems as soon as possible. Although the problem could affect some
home users, it is not considered to be a major issue for consumers,
according to Kaminsky.

At
the time he announced the flaw, Kaminsky asked members of the security
research community to hold off on public speculation about its precise
nature in order to give users time to patch their systems. Kaminsky had
planned to disclose details of the flaw during a presentation at the
Black Hat security conference set for Aug. 6.

Some researchers took the request as a personal challenge to find the flaw before Kaminsky's talk. Others complained at being
kept in the dark about the technical details of his finding.

On Monday, Zynamics.com CEO Thomas Dullien (who uses the hacker name Halvar Flake) took a guess at the bug, admitting that he knew very little about DNS.

His findings were quickly confirmed by Matasano Security, a vendor that had been briefed on the issue.

"The
cat is out of the bag. Yes, Halvar Flake figured out the flaw Dan
Kaminsky will announce at Black Hat," Matasano said in a blog posting
that was removed within five minutes of its 1:30 p.m. Eastern
publication. Copies of the post were soon circulating on the Internet,
one of which was viewed by IDG News Service.

Matasano's
post discusses the technical details of the bug, saying that by using a
fast Internet connection, an attacker could launch what's known as a
DNS cache poisoning attack against a Domain Name Server and succeed,
for example, in redirecting traffic to malicious Web sites within about
10 seconds.

Matasano
Researcher Thomas Ptacek declined to comment on whether or not Flake
had actually figured out the flaw, but in a telephone interview he said
the item had been "accidentally posted too soon." Ptacek was one of the
few security researchers who had been given a detailed briefing on the
bug and had agreed not to comment on it before details were made
public.

Matasano's post inadvertently confirmed that Flake had described the flaw correctly, Ptacek admitted.

Late Monday, Ptacek apologized
to Kaminsky on his company blog. "We regret that it ran," he wrote. "We
removed it from the blog as soon as we saw it. Unfortunately, it takes
only seconds for Internet publications to spread."

Kaminsky's attack takes advantage of several known DNS bugs, combining them in a novel way, said Cricket Liu vice president
of architecture with DNS appliance vendor Infoblox, after viewing the Matasano post.

The
bug has to do with the way DNS clients and servers obtain information
from other DNS servers on the Internet. When the DNS software does not
know the numerical IP address of a computer, it asks another DNS server
for this information. With cache poisoning, the attacker tricks the DNS
software into believing that legitimate domains, such as idg.com, map
to malicious IP addresses.

In
Kaminsky's attack a cache poisoning attempt also includes what is known
as "Additional Resource Record" data. By adding this data, the attack
becomes much more powerful, security experts say. "The combination of
them is pretty bad," Liu said.

An
attacker could launch such an attack against an ISP's domain name
servers and then redirect them to malicious servers. By poisoning the
domain name record for www.citibank.com, for example, the attackers
could redirect the ISP's users to a malicious phishing server every
time they tried to visit the banking site with their Web browser.

Kaminsky declined to confirm that Flake had discovered his issue, but in a posting to his Web site Monday he wrote
"13>0," apparently a comment that the 13 days administrators have
had to patch his flaw before its public disclosure is better than
nothing.

"Patch. Today. Now. Yes, stay late," he wrote.

He has posted a test on his Web site that anyone can run to find out if their network's DNS software is patched.

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